1. Field of the Invention
The present invention relates to self-actuating systems containing pressurized fluids, such as gas augmented air bag inflators and other stored gas products. Specifically, the invention relates to a dual-stage internal actuation system that relies on a rapid pressure differential.
2. Related Art
Many disclosures have been made in the prior art for the regulation of the flow rate of a pressurized fluid into an inflatable structure such as those employed in inflatable restraint systems used in the automotive industry for inhibiting the forward motion of a passenger during an accident or collision. A category of inflator that has recently been developed for inflating an inflatable structure, such as an air bag, is one that provides an inflation flow rate of pressurized fluid to partially inflate the structure, followed by a delayed or second increased flow rate of pressurized fluid to complete inflation of the structure. These types of inflators can be further categorized in that the second increased flow rate of fluid is accomplished by the use of differential pressures. A summary and description of the prior art employing a differential pressure to accomplish the delayed inflation of an inflatable structure is provided in U.S. Pat. No. 5,078,422 issued to Hamilton et al. on Jan. 7, 1992, and is itemized as follows:
U.S. Pat. No. 3,966,228 issued to Neuman on Jun. 29, 1976; PA1 U.S. Pat. No. 3,948,540 issued to Meacham on Apr. 6, 1976; PA1 U.S. Pat. No. 4,380,346 issued to Davis et al. on Apr. 19, 1983; PA1 U.S. Pat. No. 4,950,458 issued to Cunningham on Aug. 21, 1990; PA1 Japanese Patent 53-11433 (based on Japanese Patent Application 51-34232).
The Hamilton et al. patent (U.S. Pat. No. 5,078,422) discloses an inflator having a chamber containing a pressurized fluid for inflating an air bag. A separate differential pressure housing is provided within the chamber to actuate a percussion primer communicating with a propellant in a gas generator housing for augmenting the pressurized fluid in the chamber. In one embodiment, the differential pressure housing is divided into two compartments by a bistable pressure sensing device e.g. a cup-shaped diaphragm, which monitors the differential pressure between a pressure related to the first housing pressure and a reference pressure. Both compartments are in fluid communication with the outer housing through ports or orifices.
Efforts have also been made to incorporate devices into inflators for accommodating the use of a differential pressure for delayed flow rates of pressurized fluids to inflate confinements such as air bags. Representative of these devices include U.S. Pat. Nos. 3,910,595 and 5,078,422.